Method for the preparation of photoconductive compositions

ABSTRACT

Multiphase heterogeneous compositions are formed from an organic dye and electrically insulating polymeric material. A solution of dye and polymer is prepared and subsequently subjected to high speed shearing. Electrophotographic layers can be prepared by coating the sheared solution to form the multiphase heterogeneous compositions. Such compositions which are useful as photoconductors or electrophotosensitizers are characterized by a radiation absorption maximum that is substantially shifted from the absorption maximum of a simple, untreated solution of dye dissolved in polymer.

llnite States Patent Inventor Eugene P. Gramza Rochester, N.Y.

May 2, 1969 Oct. 26, 1971 Eastman Kodak Company Rochester, N.Y.

Continuation-impart of application Ser. No. 586,648, Oct. 14, 1966, now abandoned and a continuation-in-part of 674,006, Oct. 9, 1967, now abandoned.

METHOD FOR THE PREPARATION OF PHOTOCONDUCTHVE COMPOSITIONS 12 Claims, No Drawings 11.5. C1 96/l.6, 96/1 7, 260/37, 260/342 int. Cll G03c 5/06 lField of Search 96/16, 1.7; 252/501 Primary Examiner-George F. Lesmes Assistant Examiner-R E. Martin Att0rneys--W. H. J. Kline, J. R. Frederick and T. Hiatt ABSTRACT: Multiphase heterogeneous compositions are formed from an organic dye and electrically insulating polymeric material. A solution of dye and polymer is prepared and subsequently subjected to high speed shearing. Elec trophotographic layers can be prepared by coating the sheared solution to form the multiphase heterogeneous compositions, Such compositions which are useful as photoconductors or electrophotosensitizers are characterized by a radiation absorption maximum that is substantially shifted from the absorption maximum of a simple, untreated solution of dye dissolved in polymer.

METHOD FOR Tll-lllElPRElPARA'lllION OlF lPHOTOCONDUCTli/E (IOMPOSIITHONS This application is a continuation-in-part based on application Ser. No. 586,648, filed Oct. 14, 1966 and Ser. No. 674,006, filed Oct. 9, 1967 now both abandoned.

This invention relates to electrography and to photoconductive compositions, elements and structures useful in electrophotography In addition, this invention relates to providing novel electrophotographic compositions together with methods for their preparation and use.

Electrophotographic imaging processes and techniques have been extensively described in both the patent and other literature, for example, U.S. Pat. Nos. 2,221,776; 2,277,013; 2,297,691; 2,357,809; 2,551,582; 2,825,814; 2,833,648; 3,220,324; 3,220,831; 3,220,833 and many others. Generally, these processes have in common the steps of employing a normally insulating photoconductive element which is prepared to respond to imagewise exposure with electromagnetic radiation by forming a latent electrostatic charge image. A variety of subsequent operations, now well known in the art, can then be employed to produce a permanent record of the image.

One type of photoconductive insulating structure or element particularly useful in electrophotography utilizes a composition containing a photoconductive insulating material dispersed in a resinous material. A unitary electrophotographic element is generally produced in a multilayer type of structure by coating a layer of the photoconductive composition onto a film support previously overcoated with a layer of conducting material or the photoconductive composition can be coated directly onto a conducting support of metal or other suitable conducting material. Such photoconductive compositions have shown improved speed and/or spectral response, as well as other desired electrophotographic characteristics when one or more photosensitizing materials or addenda are incorporated into the photoconductive composition. Typical addenda of this latter type are disclosed in U.S. Pat. Nos. 3,250,615; 3,141,770 and 2,987,395. Generally photosensitizing addenda to photoconductive compositions are incorporated to effect a change in the sensitivity or speed of a particular photoconductor system and/or a change in its spectral response characteristics. Such addenda can enhance the sensitivity of an element to radiation at a particular wavelength or to a broad range of wavelengths where desired. The mechanism of such sensitization is presently not fully understood. The phenomenon, however, is extremely useful. The importance of such effects is evidenced by the extensive search currently conducted by workers in the art for compositions and compounds which are capable of photosensitizing photoconductor compositions in the manner described.

Usually the desirability of a change in electrophotographic properties is dictated by the end use contemplated for the photoconductive element. For example, in document copying applications the spectral electrophotographic response of the photoconductor should be capable of reproducing the wide range of colors which are normally encountered in such use. If the response of the photoconductor falls short of these design criteria, it is highly desirable if the spectral response of the composition can be altered by the addition of photosensitizing addenda to the composition. Likewise various applications specifically require other characteristics such as the ability of the element to accept a high surface potential, and exhibit a low dark decay of electrical charge. It is also desirable for the photoconductive element to exhibit high shoulder speed and high toe speed as measured on an electrical H and D or characteristic curve, a low residual potential after exposure and resistance to fatigue. Electrical H and D curves as referred to herein are analogous to the curves first employed by Hurter and Driffield except that voltage or surface charge on the electrophotographic element is plotted instead of density. Sensitization of many photoconductive compositions and elements containing them by the addition of certain dyes selected from the large number of dyes presently known has hitherto been widely used to provide for the desired flexibility in the design of photoconductive elements in particular photoconductive systems. Photoconductive compositions known to the art which are capable of exhibiting significant improvements in the aforementioned characteristics contain photosensitive addenda which are the subject of a copending application of William A. Light, titled NOVEL PHOTOCONDUCTlVE COMPOSITIONS AND ELEMENTS, Ser. No. 674,005, filed on Oct. 9, 1967, now abandoned. The addenda disclosed therein are responsible for the exhibition of desirable electrophotographic properties in photoconductive elements prepared therewith. Due to the need for supplying such elements, it has, therefore, become very important to establish the optimum conditions necessary for the most advantageous formation of the feature compositions so as to make maximum use of such material in the preparation of photoconductive elements.

it is, therefore, an object of this invention to provide the art of electrophotography with a novel method for the preparation of photoconductive compositions.

It is a further object of this invention to provide anew method for the formation of sensitizing addenda for use in electrophotographic compositions.

These and further objects and advantages of the present invention will become apparent from the following description and examples.

It has been discovered that many dyes and mixtures of dyes such as pyrylium dyes, including such pyrylium dyes as pyrylium, selenapyrylium and thiapyryliurn dye salts can be combined with a wide variety of electrically insulating polymeric materials to form a separately identifiable multiphase heterogeneous composition of matter useful in electrophotography. The phases of the compositions are discernable under 2500X magnification. This novel composition is more particularly characterized in the previously described copending Light application. As disclosed by Light, the feature compositions can advantageously be formed in situ in a coated photoconductive layer by contacting the layer with the vapors of an organic composition which is capable of softening the layer (e.g., exposure to the vapors immediately adjacent to the surface of a bath of dichloromethane at 70 F.). It will be further described hereinafter according to this invention that excellent control of the production of the feature composition is now achieved by the use of novel shearing techniques applied to a solution containing a polymer and dye prior to coating. The photoconducting layers coated from dopes containing sheared constituents form the feature composition without the need for further treatment.

Typically, the preparation of the feature compositions according to this invention comprises preparing a coating dope by first mixing together the constituents of the composition until dissolved. At this point, a properly prepared dope should not contain any undissolved material and therefore appears homogeneous. Coatings subsequently prepared from such an untreated dope are also homogeneous and are rendered nonhomogeneous only through the application of other preparatory means, such as vapor treatment, as disclosed by Light. In the practice of this invention, the coating of the homogeneous dope solution is preceded by the step of subjecting the solution to high speed shearing. Hereinafter, throughout the specification and claims such high speed shearing is intended to encompass stirring which is sufficiently vigorous to induce the formation ofa multiphase composition of dye and polymer when the dope is coated. A multiphase heterogeneous com position containing aggregates visible under at least 2500X magnification is thereby formed in situ in the dried film without a vapor treatment of the cast layer as described by Light. Shearing the dope prior to coating thus eliminates the need for subsequent treatment of the dried film layer. It has further been discovered that varying the length of time of such shearing will vary the size of aggregates of the discontinuous phase formed subsequently in the cast layer and also increasing the shearing time produces a smaller sized aggregate which shows an increased electrophotosensitivity over photoconductive compositions having larger aggregates.

These results are quite unexpected when it is considered that the dope both before and after the shearing step remains as a homogeneous solution. No change appears to have taken place in the character of the solution which can be attributable to the shearing. It is, therefore, surprising that the sheared solution when coated will form an electrophotographic composition having properties not possessed by an unsheared solution. Likewise, while it would be expected that prolonged shearing would reduce the individual grain size of a dispersion of particles in a liquid medium, it is unexpected that an increase in the time of shearing can reproducibly reduce the size of the aggregate contained in the feature composition subsequently formed in a cast photoconductive layer. Equally surprising is the fact that small portions of a sheared solution, when added to a similarly constituted unsheared solution and then coated, will promote the formation of a multiphase heterogeneous composition having a predictable aggregate size depending upon the size of the aggregates from the original sheared solution. Varying the time of shearing of the original or seeding solution will likewise produce a variation in the aggregate size of the multiphase composition formed when a portion of the original sheared solution is added to a similarly constituted unsheared solution and coated. The phrase similarly constituted means only that the dye, for example, in the unsheared solution is of the same general class of pyrylium type dyes and not that the dye in the unsheared solution is necessarily identical to the dye of the sheared solution.

Observable heterogeneous structure in the present photoconductive layers is indicative of the presence of the feature compositions. The presence of such compositions in the layer permits the layer to produce the hereinafter enumerated improved properties when used as a photoconductor or as a photosensitizing addendum for other photoconductors. The feature compositions when formed in situ in a layer generally have an identifiable heterogeneous appearance when viewed under at least 2500X magnification, although such compositions may appear to be substantially optically clear to the naked eye in the absence of magnification. In other compositions prepared according to the invention, there is a macroscopic heterogeneity. Suitably, the dye-containing aggregate in the discontinuous phase is predominantly in the size range of about 0.01 to 25 microns. However, it should be noted that when the heterogeneous compositions of the invention are used to sensitize a particulate photoconductor, such as zinc oxide, another discontinuous phase will be present which may not fall within this size range.

in general, the present heterogeneous compositions are two phase organic solids containing dye and polymer. The polymer forms an amorphous matrix or continuous phase which contains a discrete discontinuous phase as distinguished from a solution. The discontinuous phase contains a significant portion of the dye present and generally a predominant portion of the dye present is in the discontinuous phase. The dye in the discontinuous phase can be considered as being in particulate form; however, that phase need not be comprised wholly of dye. it is believed that in some instances the discontinuous phase may be comprised of a cocrystalline complex of dye and polymer. However, it is also believed that all of the aggregates which can be formed by the process of this invention are not necessarily comprised of both dye and polymer. Preferably, substantially all of the dye present in the system is in the discontinuous phase. When the present compositions are used in conjunction with an organic photoconductor, the resultant photoconductive composition generally contains only two phases as the photoconductor usually forms a solid solution with the continuous polymer phase. On the other hand, when the multiphase compositions prepared as described herein are used in conjunction with a particulate photoconductor, three phases may be present. In such a case, there would be a continuous polymer phase, a discontinuous phase containing dye as discussed above and another discontinuous phase comprised of the particulate photoconductor. Of course, the present multiphase compositions may also contain additional discontinuous phases.

A photoconductive layer containing the feature composition prepared according to this invention has the same exceptional electrophotographic properties as the vapor-treated layers described in the previously identified copending application. For example, the layer which is formed after shearing differs in color from the color of a similar layer formed from an unsheared dope comprising the same constituents. That is, the layer cast from a dope comprising sheared materials absorbs radiation in a different wavelength region and spectrophotometrically records absorption maxima at different wavelengths that coatings prepared from unsheared solutions. The substantial shift in radiation absorption maximum when going from an unsheared to a sheared composition is generally of the magnitude of at least about 10 mp. Similarly, a photoconductive layer prepared with the sheared dope has ag gregates in the discontinuous phase normally visible under at least 2500X magnification and exhibits an increased electrophotographic speed. The dark conductivity of the compositions formed in accordance with the invention is often lowered, and a layer containing the compositions can often be repeatedly charged and exposed with substantially no apparent electrical fatigue. The observed tendency of elements containing materials prepared by this invention to recover very rapidly after charging and exposure is important in continuous or cyclic electrophotographic applications. When such compositions are present in an electrophotographic element, the element has improved regeneration properties or an improved ability to repeatedly accept a high surface potential after completion of a charge-expose-develop (or transfer) cycle. Likewise, such photoconductive layers do no have a memory and, therefore, do not retain spurious images between charging and exposing cycles.

The theoretical basis for the novel control that shearing accomplishes in the formation and physical appearance of feature compositions is at present not fully understood. The practical result achieved when shearing conditions are changed is useful and will be more fully described hereinafter. Based on the observed changes the shearing technique appears to be broadly applicable for accomplishing the formation of multiphase heterogeneous compositions from the many constituent materials capable of forming such compositions.

In the practice of this invention a wide variety of dyes and polymeric materials are capable of forming the feature compositions and can advantageously be utilized in the shearing process for the controlled formation of heterogeneous compositions. Typically, pyrylium dyes, including pyrylium, thiapyrylium and selenapyrylium dye salts are useful in the method of forming the compositions according to this invention. Such dyes include those which can be represented by the following formula:

wherein R", R", R, R", and R can each represent (a) a hydrogen atom; (b) an alkyl group typically having from one to 15 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl, amyl, isoamyl, hexyl, octyl, nonyl, dodecyl, etc., (c) alkoxy groups like methoxy, ethoxy, propoxy, butoxy, amyloxy, hexoxy, octoxy, and the like; and (d) aryl groups including substituted aryl groups such as phenyl, 4- diphenyl, alkylphenyls as 4-ethylphenyl, 4-propylphenyl, and the like, alkoxyphenyls as 4ethoxyphenyl, 4-methoxyphenyl, 4-amyloxyphenyl, 2-hexoxyphenyl, 2-methoxyphenyl, 3,4- dimethoxyphenyl, and the like, B-hydroxy alkoxyphenyls as 2- hydroxyethoxyphenyl, 3-hydroxy-ethoxyphenyl, and the like, 4-hydroxyphenyl, halophenyls as 2,4-dichlorophenyl, 3,4- dibromophenyl, 4-chlorophenyl, 2,4-dichlorophenyl, and the like, azidophenyl, nitrophenyl, aminophenyls as 4- phenyl radicals having at least one substituent chosen from alkyl radicals of from one to six carbon atoms and alkoxy radi- 2O cals having from one to six carbon atoms;

R can be an alkylamino-substituted phenyl radical having 46 from one to six carbon atoms in the alkyl moiety including dialkylamino-substituted and halogenated alkylamino-substituted phenyl radicals;

X can be an oxygen or a sulfur atom; and

Z is the same as above.

While the pyrylium dyes are preferred in preparing the present two phase heterogeneous systems, other photographic spectral sensitizing dyes that activate light exposed areas of 52 photographic compositions can be utilized in the hydrophobic polymer of the present system.

Electrically insulating film-forming polymers suitable for 54 the formation of electrophotographic compositions containing the aggregates prepared by this invention include polycar- 55 bonates and polythiocarbonates, polyvinyl ethers, polyesters,

poly(3,3'-ethylenedioxyphenyl thiocarbonate) poly(4,4'-isopropylindendiphenyl carbonate-coterephthalate) poly(4,4'-isopropylidenediphenyl carbonate) poly(4,4'-isopropylidenediphenyl thiocarbonate) poly(2.2-butanebis-4-phenyl carbonate) poly(4.4'-isopropylidenediphenyl carbonate-blockethylcne oxide) poly(4,4'-isopropylidenediphenyl carbonate-blocktetramethylene oxide) polyl4.4"isopropylidenebis(2- methylphenyhcabonate] poly(4,4'-isopropylidenediphenyl-co-l .4-phenylene carbonate) poly(4.4'-isopropylidenediphenyl-co-l .3-phenylene carbonate) poly(4,4-isopropylidenediphenyl-eo-4.4'-diphenyl carbonate) poly(4,4'-isopropylidenediphenyl-coJA'- oxydiphenyl carbonate) poly(4,4'-isopropylidenediphenylco-4,4'-

carbonyldiphenyl carbonate) poly(4,4'-isopropylidenediphenyl-co-4 4'- ehtylenediphenyl carbonate) polyl4,4'-methylenebia(2-methylphenyl)carbonate] poly( I, I -(p'bromophenylethane )bir(4- phenyl)carbonate] poly[4,4-isopropylidenediphenyl-co-su|fonyl bisphenyl) carbonate] poly] l ,l-cyclohexane bisH- henyUcarbonate] poly(4,4'-isopropylidenediphenoxydimelhylsilane) poly[4,4'-isopropylidenebis(2- ehlorophcnyhcarbonate] polylo. a, or. or-tetramethyl-p-xylylene bis(4-phenyl carbonatfl] poly(hexafluoroisopropylidenedi-4-phenyl carbonate) poly(dichlorotetrafluoroisopropylidenedit-phenyl carbonate) poly(4,4'-isopropylidenediphenyl-4.4-

isopropylidenedibenzoatc) poly(4,4-isopropylidenedibenzyl-4.4-

isopropylidenedibenzoate) poly(4,4'-isopropylidenedi-l-naphthyl carbonate) poly]4.4'A-isopropylidene bis(phenoxy-4-pheny| sull'one)] acetophcnone-formaldehye resin poly[4.4'A-isopropylidene bis(phenoxyethyl)-co' ethylene terephthalate] phenol-forrnaldehye resin polyvinyl acetophenone chlorinated polypropylene chlorinated polyethylene poly(2.6-dimethylphenylene oxide) poly(neopentyl-2.fi-naphthnlenedicarboxylate) poly(ethylene terephthalate'co-isophthalate) poly( l ,-phenylene-co-l,B-phenylene succinate) poly(4,4'-isopropylidenedipheny| phenylphosphonate) poly(m-phenylcarboxylate) poly( l ,4-cyclohexanedimethyl terephthalate-coisophthalate poly(tetramaethylene succinate) poly(phenolphthalein carbonate) poly(4-chIoro-L3 -phcnylene carbonate) poly(Z-methyl-l.3-phenylene carbonate) poly( l ,I-bi-Z-naphthyl thiocarbonate) poly(diphenylmethane bis-4-phenyl carbonate) poly[2.2-(3-methylbutane)bis-4-phenyl carbonate poly[2.2-( 3.3-dimethylbutane)bis-4-phenyl carbonate] poly l.l-[ l-( l-naphthyl)]bis-4-phenyl carbonate} poly]2.2-(4-methylpentane)bis-4-phenyl carbonate] poly[4,4'-(2-norbornylidene)diphenyl carbonate] poly[4,4'-( hexahydro-4,7-rnethanoindan-5-ylidene) diphenyl carbonate] Especially useful polymers for forming the present heterogeneous compositions are compounds number 28,

5 30-47, 49, 51, 53,54 and 76-81 as listed in table 2 above.

Included among the preferred polymers used for preparing the two phase heterogeneous compositions of the invention including copolymers, are those linear polymers having the following recurring unit:

poly-o-olefins, phenolic resins, and the like. Mixtures of such 7 polymers can also be utilized. Such polymers include those 58 which function in the formation of the aggregates as well as 59 functioning as binders for the sensitizer and photoconductor. 40 60 Typical polymeric materials from these classes are set out in 62 table 2. 63

64 TABLE 2 65 45 66 Number Polymeric Materials 68 l polystyrene 2 poly( vinyltoluene) 50 7o 3 poly! vinylanisole) 4 polychlorostyrene 72 5 polyn-methylstyrene 73 6 polyacenaphthalene 74 7 poly! vinyl isobutyl ether) 75 8 polylvinyl cinnarnate) 5 9 poly( vinyl benzoate) 5 77 I0 polyt vinyl naphthoate) l l polyl'vinyl carbazole) 78 I2 polytvinylenc carbonate) 79 I3 polylfvinyl pyridine) 80 I4 poly( vinyl acetal) l5 poly( vinyl butyral) l6 poly(ethyl methacrylate) l7 poly( butyl methacrylate) 18 poly( styrene-co-butadiene) l9 poly(styrene-co-methyl methaerylate) 20 poly(styrene-co-ethyl acrylate) 21 poly( styrene-co-acrylonitrile) 22 poly( vinyl chloride -co-vinyl acetate) 23 poly(vinylidene ehloride-co-vinyl acetate) 24 poly(4,4'-isopropylidcnediphenyl-co-4,4'-

isopropylidenedicyclohexyl carbonate) 25 poly[LU-impropylidenebiq2,6-

s qmsta eami i 26 poly [4,4'-isopropylidenet?i(2,6-

dichlorophenyl)carbonate] 27 polyl4.4'-isopropylidenebir(2.6-

dimethylphenyl)carbonatel 28 poly( 4.4'-iwpropylidenediphenyl-co-l ,4-

cyclohexyldimethyl carbonate) 29 poly(4.4'-isopropylidenediphenyl terephthalate) wherein:

R and R when taken separately, can each be a hydrogen atom, an alkyl radical such as methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and the like including substituted alkyl radicals such as trifluoromethyl, etc., and an aryl radical such as phenyl and naphthyl including substituted aryl radicals having such substituents as a halogen, alkyl radicals of from one to five carbon atoms, etc., and R and R when taken together, can represent the carbon atoms necessary to form a cyclic hydrocarbon radical including cycloalkanes such as heiryl and polycycloalkanes such as norbornyl, the total number of carbon atoms in R and R being up to 19;

R and R can each be hydrogen, an alkyl radical of from one to five carbon atoms or a halogen such as chloro, bromo, iodo, etc., and

R is a divalent radical selected from the following:

Among the hydrophobic carbonate polymers particularly useful in accordance with this invention are polymers comprised ofthe following recurring unit:

wherein:

each R is a phenylene radical including halo substituted phenylene radicals and alkyl substituted phenylene radicals; and R, and R are described above. Such compositions are disclosed, for example, in US. Pat. Nos. 3,028,365 and 3,317,466. Preferably polycarbonates containing an alkylidene diarylene moiety in the recurring unit such as those prepared with Bisphenol A and including polymeric products of ester exchange between diphenylcarbonate and 2,2-bis(4- hydroxyphenyhpropane are used in the practice of this invention. Such compositions are disclosed in the following US. Pat. Nos. 2,999,750; 3,038,874; 3,038,879; 3,038,880; 3,106,545; 3,106,546; and published Australian Pat. Specification No. 19575/56. A wide range of film-forming polycarbonate resins are useful, particularly completely satisfactory results are obtained when using commercial polymeric materials which are characterized by an inherent viscosity of about 0.5 to 0.6. In addition, a high molecular weight material such as a high molecular weight Bisphenol A polycarbonate can be very useful. Preferably, such high molecular weight materials have an inherent viscosity of greater than about one as measured in 1,2-dichloroethane at a concentration of 0.25 g./l00 mi. and a temperature of about 25 C. The use of high molecular weight polycarbonate, for example, facilitates the formation of aggregate compositions having a higher dye concentration which results in increased speeds.

Liquids useful as solvents for preparing coating solutions to be used in the practice of this invention can include, for example, a number of organic solvents such as aromatic hydrocarbons like benzene and toluene, ketones like acetone and ethylmethyl ketone, halogenated hydrocarbons, like methylene chloride and ethylene chloride, furans like tetrahydrofuran, alkyl and aryl alcohols like methyl and ethyl, and benzyl alcohol, as well as mixtures of such solvents.

The heterogeneous compositions prepared as described herein are electrically insulating in the dark such that they will retain in the dark an electrostatic charge applied to the surface thereof. In addition, as mentioned above, the present compositions are also photoconductive. This term has reference to the ability of such compositions to lose a retained surface charge in proportion to the intensity of incident actinic radiation. In general, the term *photoconductive" as used to described the present heterogeneous compositions means that the amount of incident radiation energy in metercandle-seconds required to cause a volt reduction in retained surface potential is not greater than about 200 metercandle-seconds.

The heterogeneous compositions prepared by this invention are typically coated onto a conventional conducting support such as paper (at a relative humidity above 20 percent) including paper made more conductive by various coating and/or sizing techniques or carrying a conducting layer such as a conducting metal foil, a layer containing a semiconductor dispersed in a resin, a conducting layer containing the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer such as disclosed in U.S. Pat. Nos. 3,007,90l and 3,262,806, a thin film of vacuum deposited nickel, aluminum, silver, chromium, etc., a conducting layer as described in U.S. Pat. No. 3,245,833, such as cuprous iodide, and like kinds of conducting materials. Such conducting materials can be coated in any well-known manner such as doctor-blade coating, swirling, dip-coating, spraying, and the like. Other supports, including such photographic film bases as poly(ethylene terephthalate), polystyrene, polycarbonate, cellulose acetate, etc., bearing the above conducting layers can also be used. The conducting layer can be overcoated with a thin layer of insulating material selected for its adhesive and electrical properties before application of a photoconducting layer. Where desired, however, the photoconducting layer can be coated directly on the conducting layer where conditions permit to produce the unusual benefits described herein.

When the present two phase compositions are used as photoconductor compositions, useful results are obtained by using the described dyes in amounts of about one to about 50 percent by weight of the coating composition. When the present multiphase compositions are used as sensitizers for photoconductive coatings, useful results are obtained by using the described dyes in amounts of about 0.001 to about 30 per cent by weight of the photoconductive. coating composition, although the amount used can be widely varied. The upper limit in the amount of photoconductive composition present in a sensitized layer is determined as a matter of individual choice and the total amount of any photoconductor used will vary widely depending on the material selected, the electrophotographic response desired, the proposed structure of the photoconductive element and the mechanical properties desired in the element. Lesser amounts of the present feature material can be utilized as sensitizing amounts to increase the speed sensitivity of other photoconductors than amounts that would be used if the feature material were the only photoconductor present.

Coating thicknesses ofa photoconductive composition containing the feature compositions of the invention can vary widely Normally, a wet coating in the range from about 0.0005 inch to about 0.05 inch on a suitable support material is useful in the practice of the invention. The preferred range of wet coating thickness was found to be in the range from about 0.002 inch to about 0.03 inch.

The compositions made by the present invention can readily be used for enhancing the sensitivity and extending the spectral range of sensitivity of a variety of organic photoconductors and inorganic photoconductors including both nand ptype photoconductors. For example, these heterogeneous compositions can be used in connection with organic, including organometallic photoconducting materials which have little or substantially no persistence of photoconductivity. Representative organo-metallic compounds are the organic derivatives of Group Ila, Wu, and Va metals such as those having at least one amino-aryl group attached to the metal atom. Exemplary organo-metallic compounds are the triphenyl-p-dialkylaminophenyl derivatives of silicon, germanium, tin and lead, the tri-p-dialkylaminophenyl derivatives of arsenic, antimony, phosphorous, bismuth boron, aluminum, gallium, thallium and indium. Useful photoconductors of this type are described in copending Goldman and Johnson U.S. Pat, application Ser. No. 650,664, filed July 3, l967 and Johnson application Ser. No. 755,71 1,filed Aug. 27, 1968.

An especially useful class of organic photoconductors is referred to herein as organic amine" photoconductors. Such organic photoconductors have as a common structural feature at least one amino group. Useful organic photoconductors which can be spectrally sensitized in accordance with this invention include, therefore, arylamine compounds comprising (1) diaryl-amines such as diphenylamine, dinaphthylamine, N,N'-diphenyl-benzidine, N-phenyl-l-naphthylamine, N- phenyl-2-naphthylamine, N,N'-diphenyl-p-phenylenediamine, 2-carboxy-5-chloro-4'-methoxy-diphenylamine, panilinophenol, N,N-di-2-naphthyl-p-phenylene-diamine, those described in Fox U.S. Pat. No. 3,240,597, issued Mar. 15, 1966, and the like, and (2) triarylamines including (A) nonpolymeric triarylamines, such as triphenylamine, N,N,N'- N'-tetraphenyl-m-phenylenediamine, 4-acetyltriphenylamine, 4-hexanoyltriphenylamine, 4-lauroyltriphenylamine, 4-hexyltriphenyl-amine, 4-dodecyltriphenylamine, 4,4'-bis(diphenylamino)benzil, 4,4'-bis(diphenylamino)bensophenone and the like, and (b) polymeric triarylamines such as poly[N,4"- (N,N, N'-triphenylbensidine)], polyadipyltriphenylamine, polysebacyltriphenylamine, polydecamethylenetriphenylamina, poly-N-(4-vinylphenyl)diphenylamine, poly-N-(vinylphenylHS, B'-dinaphthylamine and the like. Other useful amine-type photoconductors are disclosed in U.S. Pat. No. 3,180,730, issued Apr. 27, 1965.

Useful photoconductive substances capable of being sensitized in accordance with this invention are disclosed in Fox U.S. Pat. No. 3,265,496, issued Aug, 9, 1966, and include those represented by the following general formula:

R- NT Q wherein T represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from one to about six carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from one to about six carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.,), an alkoxy group having from one to about six carbon atoms (e.g., methoxy, ethoxy, propoxy, pentoxy, etc.), or a nitro group; M represents a mononuclear or polynuclear monovalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc. or a substituted monovalent aromatic radical wherein said substituent can comprise a member, such as an acyl group having from one to about six carbon atoms e.g., acetyl, propionyl, butyryl, etc. an alkyl group having from one to about six carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from one to about six carbon atoms e.g. methoxy, propoxy, pentoxy, etc.), or a nitro group; O can represent a hydrogen atoms, a halogen atom or an aromatic amino group, such as MNl-l; b represents an integer from one to about 12; and, R represents a hydrogen atom, a mononuclear or polynuclear aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), a substituted aromatic radical wherein said substituent comprises an alkyl group, an alkoxy group, an acyl group, or a nitro group, or a poly(4-vinylphenyl) group which is bonded to the nitrogen atom by a carbon atom ofthe phenyl group.

Polyarylalkane photoconductors are particularly useful in producing the present invention. Such photoconductors are described in U.S. Pat. No. 3,274,000, French Pat. No.

1,383,461 and in copending application of Seus and Goldman titled PHOTOCONDUCTIVE ELEMENTS CONTAINING ORGANIC PHOTOCONDUCTORS, Ser. No. 627,857, filed Apr. 3, 1967, now U.S. Pat. No. 3,542,544. These photoconductors include leuco bases of diaryl or triaryl methane dye salts, l,l,l-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes, there being substituted an amine group on at least one of the aryl groups attached to the alkane and methane moieties of the latter two classes of photoconductors which are nonleuco base materials.

Preferred polyarylalkane photoconductors can be represented by the formula:

I J (|JE 0 wherein each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent. The aryl groups attached to the central carbon atom are preferably phenyl groups, although naphthyl groups can also be used. Such aryl groups can contain such substituents as alkyl and alkoxy typically having one to eight carbon atoms, hydroxy, halogen, etc., in the ortho, meta or para positions, ortho-substituted phenyl being preferred. The aryl groups can also be joined together or cyclized to form a fluorene moiety, for example. The amino substituent can be represented by the formula wherein each L can be an alkyl group typically having one to eight carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group typically having five to six atoms in the ring such as morpholino, pyridyl, pyrryl, etc. At least one of D, E, and G is preferably p-dialkylaminophenyl group. When J is an alkyl group, such an alkyl group more generally has one to seven carbon atoms.

Representative useful polyarylalkane photoconductors include the compounds listed in table 3.

TABLE 3 dimethyltriphenylmethane 4',4" -bis(dimethylamino)-2',2"-dimethyl-4- methoxylriphenylmethane bis(4-dierhylamino)ietraphenylrnethane bis(4-diethylamino)telraphenylmethane 4,4"-bis(benzylethylamino)-2',2"-

dimethyltriphenylmethane 4',4"-bis(diethylamino)-Z',2"- dimethyltriphenylmethanc 4,4'-bis(dimethylamino)- l l ,l-triphenylethnne l-(4-N,N-dimelhylnminophcnyl)-l ,l-diphenylcthane 4-dimethylaminotetraphenylmethane ll l2 18 -diethylam inotetraphenylmethane Another class of photoconductors useful in this invention are the 4-diarylamino-substituted chalcones. Typical com pounds of this type are low molecular weight nonpolymeric ketones having the general formula:

wherein R and R are each stituted phenyl radicals and radical having the formula:

phenyl radicals including subparticularly when R is a phenyl The following table 4 comprises a partial listing of U.S. Patents disclosing a wide variety or organic photoconductive compounds and compositions which can be improved with respect to speed, sensitivity, and/or regeneration when incorporated into the feature compositions and elements of this inventlon.

TABLE 4 Inventor U.S. Pat, No.

Hoegl et al. 3,037,861 Sues et al. 3,041,165 Schlesinger 3,066,023 Bethe 3,072,479 Klupfel et a1. 3,047,095 Neugebauer et al. 3,112,197 Cassiers et a1, 3,133,022 Schlesinger 3,144,633 Noe er a1. 3,122,435 Sues et a1 3,127,266 Schlesinger 3,130,046 Cassiers 3,131,060 Schlesinger 3,139,338 Schlesinger 3,139,339 Cassicrs 3,140,946 Davis et al. 3,141,770 Ghys 3,148,982 Cassiers 3.155.503 Cassiers 3,158,475 Tomanek 3,161,505 Schlesinger 3,163,530 Schlesinger 3,163,531 Schlesinger 3,163,532 Hoegl 3,169,060 Stumpf 3,174,854 Klupfel et al. 3,180,729 Klupfel et al. 3,180,730 Neugebauer 3,189,447 Neugebauer 3,206,306 Fox 3,240,597 Schlesinger 3,257,202 Sues et al. 3,257,203 Sues et al. 3,257,204 Fox 3,265,496 Kosche 3,265,497 Noe et a1. 3,274,000

The compositions of the present invention can be employed in photoconductive elements useful. in any of the well-known electrophotographic processes which require photoconductive layers. One such process is the xerographic process. In a process of this type, an electrophotographic element held in the dark is given a blanket electrostatic charge by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial dark insulating property, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then selectively dissipated from the surface of the layer by imagewise exposure to light by means ofa conventional exposure operation such as, for example, by a contact-printing technique, or by lens projection of an image, and the like, to thereby form a latent electrostatic image in the photoconductive layer. Exposing the surface in this manner forms a pattern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the intensity of the illumination in a particular area.

The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charged or uncharged areas rendered visible, by treatment with a medium comprising electrostatically responsive particles having optical density. The developing electrostatically responsive particles can be in the form of a dust, i.e., powder, a pigment in a resinous carrier, i.e., toner. A preferred method of applying such toner to a latent electrostatic image for solid area development is by the use of a mag netic brush. Methods of forming and using a magnetic brush toner applicator are described in the following U.S. Pat. Nos. 2,786,439; 2,786,440; 2,786,441; 2,811,465; 2,874,063; 2,984,163; 3,040,704; 3,1 17,884; and Reissue 25,779. Liquid development of the latent electrostatic image may also be used. In liquid development the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature, for example, U.S. Pat. No. 2,296,691 and in Australian Pat. No. 212,315. In dry developing processes the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one ofits components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after development and fusing, Techniques of the type indicated are well known in the art and have been described in a number of U.S. and foreign patents, such as U.S. Pat. No. 2,297,691 and 2,551,582 and in RCA Review," Vol. 15 (1954) pages 469-484.

Processes such as described hereinbefore have found utility where the photoconductive layer is either inexpensive and expendable such as the various processes using photoconductive zinc oxide, or where the photoconductive media is rapidly reusable such as vitreous selenium. Many of the feature compositions of this invention now permit a large number of known photoconductive compounds and compositions to be employed in xerographic processes where rapid repeated charging and exposing is desired.

The method of this invention is typically practiced as described in detail in the following examples.

EXAMPLE 1 A photoconductive coating composition is prepared by dissolving 300 g. of a polycarbonate resin, a composition formed from the reaction between phosgene and a dihydroxydiarylalkane or from the ester exchange between diphenylcarbonate and 2,2-bis-4-hydroxyphenylpropane (Lexan 105 polycar- TABLE 5 bonate resin, General Electric Company), 200 g. of 4,4- Spged benzyhdenebrs (N,N-d1ethyl -m-tolu1d1ne) and 10 g. of 4-(4- 2: 3; dimethylammophenyl)-2,6-d1phenylth1apyryl1um perchlorate time, Aggregate Sm in 1700 g. of methylene chloride and 1133.3 g. of 1,1,2- minutes (microns) Neg P05 Neg trichloroethane. This mixture is thoroughly dissolved after 2 1) 15 5 r. 6,500 80 1,800 hours of stirring. The resulting solution is then sheared by g;::: 2g 3-"- g fi g g placing the solution in a high-speed shearing blender and (4)...-.. 60 1 :02... 6,300 2,000 2,000 shearing for a period of time. Samples of the solution are 82: figg 'x 21% 21% 5% 2% withdrawn from the blender at various times during the shearing and each sample is coated at a dry coverage of 0.7 g./ft. EXAMPLE 2 from an extrusion hopper. The coating from the hopper is laid on a polyester film support which has previously been over- A solution prepared as described in example 1 is divided coated with two other layers. The layer next to the film supinto three equal parts prior to shearing. For purposes of port isaconducting layer comprising cuprous iodide in a resin identification two of the parts (a) and (b) are not sheared binder. The layer overcoating the conducting layer is an insuprior to coating. The third part (c) is sheared for 4 hours in a lating barrier layer of cellulose nitrate. After drying the high speed blender as in example 1 prior to coating. To insure separate coatings are visually examined. Each of the coatings the formation of multiphase heterogeneous composition in shows the characteristic color and granular appearance of the each case the coatings from (a) and (b) are vapor treated for 5 formation of the feature composition. This examination also and 2 minutes respectively in the vapors of a bath of reveals that the samples which have undergone longer sheardichloroethane at 70 F. The results of aggregate size meaing times formed coatings having smaller aggregates than the surement after the various treatments, the electrophotoaggregates formed in coatings prepared from dopes which graphic shoulder and toe speed and the resolving power in have been sheared for shorter periods of time. In addition, in- 2 5 lines per millimeter of the coatings when charged, exposed to creasing the length of time of shearing produces a change in a positive microimage and developed with a liquid developer the electrophotographic speeds of the various coatings. These in the manner described in U.S. Pat. No. 2,907,674 are speed changes are summarized in table 5. The actual positive recorded in table 6.

TABLE 6 Speed Aggregate Shoulder 50 v. toe

Solution Shearing sizc Resoused timc,hours (microns) Pos. Neg. Pos. Neg. lution (21).. None 5m 10.. 7,000 7,000 10 1,800 15 (b). t None 1t02 8,000 6,300 1,800 1,700 136 (c)v 4 Ab0ut0.1 t 8,000 6,700 2,000 1,800 250 or negative electrical speeds of the coatings (as shown in table The data recorded in table 6 clearly shows the effect of sheart 5) are determined in the following manner. An element as ing on the formation of the heterogeneous composition in the described above is electrostatically charged under a corona coating and upon the electrophotographic properties of the source until the surface potential, as measured by an eleccoatings. Particularly advantageous is the observation that the trometer probe, reaches about 600 volts, positive or negative. formation of smaller aggregate sizes, which would be expected The charged element is then exposed to a 3000 K. tungsten to promote higher resolution and optical clarity in the coating, light source through a stepped density gray scale. The expoalso permits high electrophotographic speeds to be realized. sure causes reduction of the surface potential of the element EXAMPLE 3 under each step of the neutral density scale from its initial potential, V,,, to some lower potential, V, whose exact value A coating composition is prepared as in example 1 and didepends on the actual amount of exposure in meter-candlevided into three parts prior to shearing. The separate composiseconds received by the area. The results of these measurctions are sheared as in examples l and 2 for 30 min., 60 min., ments are then plotted on a graph of surface potential V vs. and 90 min. Each sheared composition is then added to log exposure for each step. The actual positive speed of the separate unsheared solutions prepared in the same manner element can then be expressed in terms of the reciprocal of each comprising 10 times the volume of each sheared soluthe exposure required to reduce the surface potential to any tion. The new solutions I, ll and Ill contain, respectively, the arbitrarily selected value. Herein, unless otherwise stated, the 30 min. (I), min. (II) and min. (lll) sheared conactual electrical speed is the numerical expression of IO distituents. Solutions 1, ll and Ill are coated as in example 1 and vided by the exposure in meter-candle-seconds required to the results are recorded in table 7.

TABLE 7 Speed Shoulder 60 v. toe Shear, Aggregate size e Reso- Solution min. (microns) los Neg. Pos Neg. lution 1 (III)..... 00 Ahout.1to.2 7,000 6,300 2,000 2,000 250 1 I/mm.

reduce the 600 volt charged surface potential to a value of 500 70 The electrophotographic speed and resolution of the coatings volts volt shoulder speed) or to 50 volts (50 volt toe speed). All of the sheared or heterogeneous coatings prepared as above can be toned to produce visible images after being charged and imagewise exposed, typical suitable toners being disclosed in U.S. Reissue Pat. No, 25,136.

reported in table 7 correspond closely to the results obtained where the entire coating dope was sheared prior to coating (see table 5). It is apparent from these results that the addition of small amounts of sheared material to a larger volume of material capable of forming a heterogeneous composition in the coating, is sufficient to initiate such formation. It is also interesting to observe that the resultant aggregate size in the discontinuous phase of the dried coating is of the same order of magnitude as the aggregate size that could be expected from the shearing time of the added material. Close control of aggregate size within large volumes of coating dope can, therefore, be simply accomplished using sheared dope additions which have been classified by their ability to form certain sized aggregates.

EXAMPLE 4 The procedure of example 1 is generally repeated using as the sensitizer 0.4 g. of 4-(4-dimethylaminophenyl)-2,6- diphenylthiapyrylium perchlorate in place of the 4-[4-bis(2- chloroethyl)-aminophenyl]'2,fi-diphenylthiapyrylium perchlorate. The poly-carbonate resin, the photoconductor and the sensitizer are dissolved in a solvent mixture of 52.5 g. of dichloromethane and 52.5 g. of l,2-dichloroethane by stirring the solids in the solvent for 2 hours at about 70 F. The resulting solution is then sheared for 20 minutes in a high speed shearing blender while maintaining the temperature of the solution at about 50 F. The sheared solution is then coated onto a conducting substrate. The substrate consists of an evaporated nickel film coated on Estar film base which is subbed with a terpolymer of2 weight percent itaconic acid, 13 weight percent methyl acrylate and 85 weight percent vinylidene chloride. The net density of the evaporated nickel film is about 0. l and the resistivity of the substrate is about 103 ohm/sq. This coating absorbs 94 percent of the incident radiation at the absorption peak of 675 p.. The electrophotographic element formed above is repeatedly charged to a positive or negative 600 v. potential and photodischarged to determine the resistance of the coating to electrical fatigue. After 1000 such cycles at a time interval of 3 seconds between photodischarging and recharging, the coating will still accept a high surface charge under the same charging conditions. This indicates that the coating has excellent regeneration properties. The positive and negative 100 v. toe speeds measured in a manner similar to that in example 1 are 3,200 and 3,500, respectively. The densities and resistivities of other metal conducting substrates such as titanium, nichrome, stainless steel, etc., as well as the regeneration properties, speeds and absorption of other organic photoconductive coatings which are coated directly on these metal substrates compare favorably with the above values.

EXAMPLE 5 Nine parts by weight of the polymer of example 1, six parts by weight of the photoconductor of example 1 and 0.3 parts by weight of the dye 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyryliurn fluoroborate are dissolved in 85 parts by weight of dichloromethane. Ten percent of the resultant solution is placed in a high shear blender and sheared for about one-half hour. The sheared solution is then added to the unsheared portion, thoroughly mixed and the combined solution is coated on a conducting support as in example 4. The dry thickness of the coating is about l0-l2;z. When viewed under magnification, the coating has a granular appearance. The resultant electrophotographic element is measured for speed as in example 1 with the exposure being changed slightly by the addition of a short wavelength pass interference filter having percent transmittance at 600 p. The negative 50 volt toe speed is 800 as compared to a speed ofless than 50 for a similar element having a homogeneous coating of the same constituents which were not sheared.

EXAMPLE 6 A coating dope is prepared by dissolving 60 parts by weight of the binder of example 1, 40 parts by weight of the photoconductor of example 1 and four parts by weight of the dye 2-ethoxyphenyl-4-dimethylaminophynyl-6-phenylthiapy rylium perchlorate in methylene chloride with gentle stirring.

The dope is then coated as in example 1 to form a control element. Next, I00 parts by weight of the binder of example 1 and 0.015 parts by weight of the dye of example 1 are dissolved in methylene chloride and the solution is subjected to high shear for a period of 30 minutes while maintaining the solution at 70 F. A 2 ml. portion of this sheared solution is added to a coating dope containing the constituents of the control followed by stirring. The combined solution is coated as above to form an electrophotographic element having an aggregate photoconductive layer thereon. The negative I00 v. toe speed of the element having the heterogeneous layer is 630 as compared to the negative v. toe speed of 5.5 for the homogeneous control coating.

An improvement in electrophotographic properties similar to that shown in the preceding examples can be obtained when other dyes of the types described herein are incorporated into electrophotographic compositions prepared according to this invention. The control over the formation of the heterogeneous compositions as characterized herein is observed when these dyes are associated with polymeric materials according to the method of this invention. The heterogeneous compositions of this invention can readily be formed separately and then added to a suitable photoconductor. However, in order to reduce the necessary shearing time required to produce a given size aggregate, it is often advantageous to shear the dye and polymer in the presence of the photoconductor. In this manner, the shearing time can be reduced and the subsequent step of adding the heterogeneous. composition to the photoconductor can be eliminated.

It will be apparent from the foregoing examples and description that the method ofthis invention permits the effective formation of electrophotographic compositions which can be utilized in photoconductive elements of many structural variations.

Likewise it should be apparent from the foregoing description and examples that no single form of shearing mechanism is essential for the effective preparation of heterogeneous compositions. Many commercially available high-speed shearing devices are well suited for use in practice of the present invention and exemplary devices are sold under such trade names as Gaulin Homogenizer, Cowles Dissolver, Premier Mill Dipersator, etc. The effectiveness of any device selected may be easily ascertained without undue experimentation by preparing sample coatings as described herein and inspecting the coatings for the formation of the feature compositions. Electrophotographic data will also help in determining the optimum combinations of conditions necessary to obtain the results desired.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

lclaim:

l. A method for forming a heterogeneous photoconductive composition comprising the steps of dissolving in an organic solvent a pyrylium dye and polymeric material having an alkylidene diarylene moiety in the recurring unit, shearing said solution such that a coating prepared from said sheared solution is heterogeneous and absorbs radiation at a wavelength maximum at least 10 u different from the wavelength of maximum absorption of an identical coating prepared from an unsheared solution containing the same constituents, forming a coating of said sheared solution, and drying said coating to form a heterogeneous composition comprising a continuous phase of said polymeric material and a discontinuous phase comprising a combination of said dye and polymeric material.

2. A method for producing a heterogeneous photoconductive insulating composition comprising the steps of preparing a solution of an electrically insulating polymeric material having an alkylidene diarylene moiety in the recurring unit and a pyrylium dye selected from the group consisting of pyrylium, thiapyrylium and selenapyrylium dye salts, subjecting said solution to high-speed shearing for an interval of time, coating a thin layer of said solution and allowing said layer to dry to form a heterogeneous organic solid comprising a continuous phase of polymeric material having dispersed therein a discontinuous phase containing a combination of said polymeric material and dye, said shearing being performed for an interval of time at least sufficient to initiate the formation of a heterogeneous organic solid when coated and dried.

3. A method as described in claim 1 wherein electrically insulating polymeric material is a carbonate polymer and wherein said discontinuous phase is visible under at least 2SO0X magnification.

4. A method for preparing a heterogeneous photoconductive composition comprising the steps of dissolving in an organic solvent a pyrylium dye and an electrically insulating, film-forming polymeric material having an alkylidene diarylene moiety in the recurring unit, shearing the resultant solution at least until a test coating prepared from a portion of such solution forms a heterogeneous photoconductive layer having a maximum absorption at least mp. different from the wavelength of maximum absorption of a test coating prepared from an unsheared portion of such solution, adding said sheared solution to a larger volume of a similarly constituted unsheared solution, coating the combined solutions and drying to form a heterogeneous composition comprising a continuous phase of polymeric material having dispersed therein a discontinuous phase comprising a combination of said dye and polymeric material.

5. A method for preparing an electrophotographic element comprising the steps of dissolving a pyrylium dye and a polycarbonate resin having an alkylidene diarylene moiety in the recurring unit in an organic solvent, shearing the resultant solution at least until a test coating prepared from a portion of said sheared solution forms a heterogeneous photoconductive layer having an absorption maximum at least 10 mp. different from the absorption maximum of a coating prepared from an unsheared portion of said solution, adding the sheared solution to a larger volume of a similarly constituted unsheared solution of a pyrylium dye and a polymeric material having an alkylidene diarylene moiety in the recurring unit, coating the combined solutions in a thin layer on a conductive support and drying said layer to form an electrophotographic element having a layer of a heterogeneous photoconductive composition comprising a continuous binder phase of polymeric material having dispersed therein a particulate discontinuous phase comprising a combination of said dye and polymeric material.

6. The method as described in claim 5 wherein the unsheared solution to which the sheared solution is added consists essentially of an organic solvent, a pyrylium dye, an electrically insulating, film'forming polymeric material having an alkylidene diarylene moiety in the recurring unit and an organic photoconductor.

7 The method of claim 1 wherein the electrically insulating polymeric material is a hydrophobic polymer having an alkylidene diarylene moiety in the recurring unit and wherein said discontinuous phase is visible under at least 2500X magnification.

8 The method of claim 1 wherein a photoconductive compound is added to said solution prior to shearing.

9 The method ofclaim 1 wherein the dye has the formula:

wherein:

R and R are aryl radicals selected from the group consisting of phenyl and substituted phenyl having at least one substituent selected from the group consisting of an alkyl radical of from one to six carbon atoms and an alkoxy radical of from one to six carbon atoms;

R is an alkylamino-substituted phenyl radical having from one to six carbon atoms in the alkyl moiety;

X is selected from the group consisting of sulfur and oxygen;

and

2 is an anion; and wherein the polymeric material contains the following recurring unit;

wherein:

R is a phenylene radical and each of R, and R when taken separately, is selected from the group consisting of a hydrogen atom, an alkyl radical of from one to 10 carbon atoms and a phenyl radical and R, and R when taken together, are the carbon atoms necessary to form a cyclic hydrocarbon radical, the total number of carbon atoms in R and R being up to l9.

10. The method of claim 1 wherein the dye is selected from the group consisting of 4-(4-dimethylaminophenyl)-2,6- diphenylthiapyrylium perchlorate; 4-(4-dimethylaminophenyl)-2,o-diphenylthiapryrylium fluoroborate; 4-[4-bis(2- chloroethyl)aminophenyl]2,6-diphenylthiapyrylium perchlorate; 4-(4-dimethylaminophenyl)-2,o-diphenylthiapyrylium p-toluenesulfonate; 4-(4-dimethylaminophenyl)-2,6- diphenylpyrylium perchlorate; 4-(4-dimethylaminophenyl)- 2,6-bis(4-ethylphenyl )thiapyrylium perchlorate; 4-(4 dimethylamino-2-methylphenyl )-2,6'diphenylpyrylium perchlorate 2-(4-methoxyphenyl)-4-[4-bis (2- chloroethyl)aminophenyl]6-phenylthiapyrylium perchlorate; 2-(4-methoxyphenyl)-4-(dimethylaminophenyl)-6-phenylthiapryrylium perchlorate; 2-(4-ethoxyphenyl)-4- (dimethylaminophenyl)-6-phenylthiapyrylium per chlorate; 4- (4-dimethylaminophenyl)-2,-diphenylthiapyrylium sulfate; and 4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium ptoluenesulfonate.

11. The method of claim 3 wherein the dye of the sheared solution is selected from the group consisting of pyrylium and thiapyrylium dye salts and wherein the polymeric material of said sheared solution is a carbonate polymer.

12. The method of claim 3 wherein the unsheared solution to which the sheared solution is added comprises a solvent, a pyrylium dye, a hydrophobic polymer having an alkylidene diarylene moiety in the recurring unit and an organic photoconductor.

i n t e n:

" UNITED STATES PATENT OFFICE (569) CERTIFICATE OF CORRECTION Patent No. 3 615 c 5 Dated October 26 197i Inventor(s) Eugene P. Gramza It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 18 line 62 delete "10%" and insert ---l0 m/a Column 20 in the first formula, insert -Z' as illustrated below:

I R1 R Column 20 line 17 delete "2 and insert -Z in the second formula, delete r! and insert therefor a single bond line line 55 after "salts" insert wherein said unshe ared solutior contains a dye selected from the group consisting of pyryl ium and thiapyrylium dye s alts- Signed and sealed this 1 8th day of July 1 972.

iShAL} fittest:

' DWARD M.FLETCHER,JR. ROBERT GOTTSCHALK J ttesting Officer Commissioner of Patents 

2. A method for producing a heterogeneous photoconductive insulating composition comprising the steps of preparing a solution of an electrically insulating polymeric material having an alkylidene diarylene moiety in the recurring unit and a pyrylium dye selected from the group consisting of pyrylium, thiapyrylium and selenapyrylium dye salts, subjecting said solution to high-speed shearing for an interval of time, coating a thin layer of said solution and allowing said layer to dry to form a heterogeneous organic solid comprising a continuous phase of polymeric material having dispersed therein a discontinuous phase containing a combination of said polymeric material and dye, said shearing being performed for an interval of time at least sufficient to initiate the formation of a heterogeneous organic solid when coated and dried.
 3. A method as described in claim 1 wherein electrically insulating polymeric material is a carbonate polymer and wherein said discontinuous phase is visible under at least 2500X magnification.
 4. A method for preparing a heterogeneous photoconductive composition comprising the steps of dissolving in an organic solvent a pyrylium dye and an electrically insulating, film-forming polymeric material having an alkylidene diarylene moiety in the recurring unit, shearing the resultant solution at least until a test coating prepared from a portion of such solution forms a heterogeneous photoconductive layer having a maximum absorption at least 10 m Mu different from the wavelength of maximum absorption of a test coating prepared from an unsheared portion of such solution, adding said sheared solution to a larger volume of a similarly constituted unsheared solution, coating the combined solutions and drying to form a heterogeneous composition comprising a continuous phase of polymeric material having dispersed therein a discontinuous phase comprising a combination of said dye and polymeric material.
 5. A method for preparing an electrophotographic element comprising the steps of dissolving a pyrylium dye and a polycarbonate resin having an alkylidene diarylene moiety in the recurring unit in an organic solvent, shearing the resultant solution at least until a test coating prepared from a portion of said sheared solution forms a heterogeneous photoconductive layer having an absorption maximum at least 10 m Mu different from the absorption maximum of a coating prepared from an unsheared portion of said solution, adding the sheared solution to a larger volume of a similarly constituted unsheared solution of a pyrylium dye and a polymeric material having an alkylidene diarylene moiety in the recurring unit, coating the combined solutions in a thin layer on a conductive support and drying said layer to form an electrophotographic element having a layer of a heterogeneous photoconductive composition comprising a continuous binder phase of polymeric material having dispersed therein a particulate discontinuous phase comprising a combination of said dye and polymeric material.
 6. The method as described in claim 5 wherein the unsheared solution to which the sheared solution is added consists essentially of an organic solvent, a pyrylium dye, an electrically insulating, film-forming polymeric material having an alkylidene diarylene moiety in the recurring unit and an organic photoconductor.
 7. The method of claim 1 wherein the electrically insulating polymeric material is a hydrophobic polymer having an alkylidene diarylene moiety in the recurring unit and wherein said discontinuous phase is visible under at least 2500X magnification.
 8. The method of claim 1 wherein a photoconductive compound is added to said solution prior to shearing.
 9. The method of claim 1 wherein the dye has the formula:
 10. The method of claim 1 wherein the dye is selected from the group consisting of 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate; 4-(4-dimethylaminophenyl)-2,6-diphenylthiapryrylium fluoroborate; 4-(4-bis(2-chloroethyl)aminophenyl)-2,6-diphenylthiapyrylium perchlorate; 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium p-toluenesulfonate; 4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium perchlorate; 4-(4-dimethylaminophenyl)-2,6-bis(4-ethylphenyl)thiapyrylium perchlorate; 4-(4-dimethylamino-2-methylphenyl)-2,6-diphenylpyrylium perchlorate 2-(4-methoxyphenyl)-4-(4-bis (2-chloroethyl)aminophenyl)-6-phenylthiapyrylium perchlorate; 2-(4-methoxyphenyl)-4-(dimethylaminophenyl)-6-phenylthiapryrylium perchlorate; 2-(4-ethoxyphenyl)-4-(dimethylaminophenyl)-6-phenylthiapyrylium per chlorate; 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium sulfate; and 4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium p-toluenesulfonate.
 11. The method of claim 3 wherein the dye of the sheared solution is selected from the group consisting of pyrylium and thiapyrylium dye salts and wherein the polymeric material of said sheared solution is a carbonate polymer.
 12. The method of claim 3 wherein the unsheared solution to which the sheared solution is added comprises a solvent, a pyrylium dye, a hydrophobic polymer having an alkylidene diarylene moiety in the recurring unit and an organic photoconductor. 